Severe asthma in children is a complex disorder characterized by persistent airway inflammation, ongoing symptoms and extreme morbidity despite treatment with high doses of inhaled corticosteroids. While the pathophysiology of severe asthma is poorly understood, affected children have profound airway oxidant stress associated with disturbances in the oxidizing and reducing (redox) environment. While the clinical ramifications of this oxidant stress are unclear, these disturbances cannot be benign. This study is designed to answer the important clinical question whether corticosteroid sensitivity is altered in children with severe asthma. This study will further determine how airway redox disturbances regulate the response to corticosteroids in children with severe asthma. The hypothesis is that airway redox disturbances inhibit corticosteroid sensitivity through oxidation of the glucocorticoid receptor. To test this hypothesis, the intramuscular corticosteroid, triamcinolone, will be administered to children with severe asthma from the metropolitan Atlanta area who remain symptomatic despite treatment with high doses of inhaled corticosteroids. Corticosteroid insensitivity will be defined as <15% improvement in the forced expiratory volume in one second 4 weeks after triamcinolone administration. The specific aims of this project are: 1) to determine the clinical pattern and prevalence of corticosteroid insensitivity; 2) to determine whether altered airway redox status predicts corticosteroid insensitivity; and 3) to determine whether oxidation of the glucocorticoid receptor is a mechanism of corticosteroid insensitivity in children with severe asthma. The studies presented here will provide critically-needed data to advance the field of severe asthma in children. Although corticosteroids are the cornerstone of asthma treatment, there is very little evidence supporting the use of high doses of corticosteroids in children with severe asthma. New knowledge derived from these aims will demonstrate for the first time whether corticosteroid insensitivity is a true feature of severe asthma in children and whether airway redox disturbances account for this phenomenon. The long-term goal of this research is to utilize these data to develop novel antioxidant interventions to reverse corticosteroid insensitivity in children with severe asthma. The data generated here may therefore improve clinical outcomes in this highly challenging group of children with severe asthma for whom there are very few therapeutic alternatives.